Electroplating of Carbon Nanotube Yarns and Tapes with Five Metals
Carbon nanotube (CNT) tapes and yarns can reduce the weight of industrial cables for aviation and space by substituting for copper. In order to attach CNTs to connectors, one high-reliability method of attachment is soldering, which is difficult; however it can be facilitated by electroplating. In this study, CNT tapes and yarns were plated with Cu, Ag, Ni, Sn and Au.
Materion Large Area Coatings
Windsor, Connecticut, USA
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Carbon nanotube (CNT) tapes and yarns can reduce the weight of industrial cables for aviation and space by substituting for copper. In order to attach the CNTs to cable connectors, one high-reliability method of attachment is soldering. Soldering to CNTs is extremely difficult; however it is facilitated by electroplating the CNT with solderable metals. In this study, CNT tapes and yarns were electroplated with copper, silver, nickel, tin and gold. Electrodeposition rates of CNT yarns were 5.5, 3.9, 6.7, 19.9, and 0.64 μm/min, on copper, silver, nickel, tin and gold, and on CNT tapes similar numbers scaled down by area. Best surface treatment, current, loading, temperature, concentration, additives, correct anode, and their effect on efficiency, deposition rate and adhesion were determined. Adhesion of copper films improved markedly over 15 μm thickness. Multiple samples of up to five at a time were deposited by scaling up the current by the number of samples. The Cp value was 3.4 for copper, indicating copper plating was repeatable.
Keywords: CNT, carbon nanotube, electroplating, adhesion, SPC, current efficiency, soldering, attachment.
Carbon nanotubes (CNTs) are a widely studied allotrope of carbon. Their size-to-length ratio creates unique physical properties, such as tensile strength and conductivity, which outperform common bulk materials. Possible applications of CNTs are energy storage, interconnects for CMOS and sensors.1 Military and commercial aircraft and satellites have miles of cable that are used for transmitting signals and power. Carbon nanotube (CNT) tapes and yarns are lightweight conductive materials that show potential for signal and current carrying capacity. These light-weight materials could enable military and commercial aircraft and satellites to travel further on less fuel. By replacing copper in a cable with CNT materials, the weight of a cable assembly can be reduced 70%.2 While mechanical crimps are an adequate termination strategy, soldering directly onto the CNT materials is not possible due to their hydrophobicity.3,4 By metallizing the CNT via electroplating and/or electroless plating metals, soldering is possible. TE Connectivity** is researching the replacement of copper in cable assemblies, and has already used CNTs for USB cables.
Discovery and demonstration
The first mention of a carbon filament from the decomposition of methane is credited to Edison in 1889 in an electric light bulb patent.5 The first TEM image of tubular carbon filaments was published in Russian (Fig. 1).6 Iijima7 is given credit for demonstrating the presence of CNTs in the cathode arc in electric arc trials intended to create fullerenes (C60). A survey article of the history of carbon nanotubes, graphene and fullerenes appeared in Carbon in 2006.6 The authors discuss the almost simultaneous identification of single-walled CNTs (SWCNTs) at IBM by Bethune8 in 1993, and Iijima and Ichihashi,7 published a month earlier.